JP2002082302A - Optical scanning method, optical scanner, photosensitive medium, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the image forming state of a deflected beam in the main and the sub-scanning directions and to control image forming position in both the main and sub-scanning directions. SOLUTION: In an optical scanning method for deflecting one or more beams radiated from a light source 1 with a scanning optical system, forming one or more optical spots on a photosensitive medium 7 and conducting optical scanning by one or more scanning lines, an optical transmittance detection pattern 70 formed as part of the medium 7 on an area, other than the image forming area of the medium 7 to detect the deviation between an image-forming position in the main scanning direction and sub-scanning direction of the deflected beams and the surface of the medium 7 is optically scanned by the defected beams, to detect a change of transmitted light due to the detection pattern 70, and the deviation between the image forming position of the deflected beams and the surface of the medium 7 is corrected independently in each of the main scanning direction and the sub-scanning direction to conduct optical scanning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical scanning method, an optical scanning device, a photosensitive medium, and an image forming apparatus.

[0002]

2. Description of the Related Art In recent years, in an image forming apparatus using an optical scanning device such as a digital copying machine or a laser printer, a reduction in the diameter of a light spot on a surface to be scanned has been required with the increase in the density of optical writing. ing. In response to such a demand, 30μ
A light spot diameter of about m is being put to practical use. But,
On the other hand, when the diameter of the light spot is reduced, there is a problem that the accuracy of parts and the assembling system become strict. For example, when the light spot diameter is set to about 30 μm as described above, a mechanical error margin (so-called depth margin) for the actual light spot diameter to fall within a range of about 30 ± 3 μm.
Is only about 1 mm, and it is not always easy to keep the component accuracy and the assembly accuracy within such a margin. Therefore, as a method of detecting the image forming state of the deflected light beam and adjusting the image forming position with respect to the surface to be scanned, a method of adjusting the image forming position of the deflected light beam by using a light beam from a light source and a subsequent optical system A method of displacing the coupling lens to be coupled to the optical axis in the direction of the optical axis has been proposed (JP-A-2-2898).
No. 12, JP-A-10-142546). However, the optical system of the optical scanning device generally has a different imaging function between the main scanning direction and the sub-scanning direction, and even if the coupling lens is adjusted in the optical axis direction, the image forming position in the main scanning direction is changed. And the imaging position in the sub-scanning direction cannot always be adjusted simultaneously. Further, the detecting means described in the above publication can detect the image forming state in the main scanning direction, but cannot detect the image forming state in the sub-scanning direction. In recent years, a so-called “multi-beam scanning method” in which light scanning is performed using a plurality of light beams in order to increase the speed of light scanning.
However, in the multi-beam scanning method, a good image cannot be formed unless the scanning line pitch, which is the interval between scanning lines formed by adjacent light spots in the sub-scanning direction, is not appropriate. Therefore, in the multi-beam scanning method, it is preferable that the scanning line pitch can be detected.

[0003]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention detects the imaging state of a deflected light beam in the main scanning direction and the sub-scanning direction, and adjusts the imaging position in the main scanning direction and the sub-scanning direction. The task is to make it possible.

Another object of the present invention is to make it possible to easily detect a scanning edge pitch in a multi-beam scanning system.

[0005]

According to a first aspect of the present invention, there is provided an optical scanning method comprising the steps of: "deflecting one or more light beams emitted from a light source by a scanning optical system and forming one or more light spots on a photosensitive medium. And an optical scanning method for optically scanning one or more scanning lines ", and has the following features. That is, "a light transmission detection pattern for detecting a deviation between the image forming position of the deflected light beam in the main scanning direction and the sub-scanning direction and the surface of the photosensitive medium" indicates that the photosensitive medium is out of the image forming area of the photosensitive medium. It is formed as a part. This detection pattern is optically scanned with a deflected light beam, and a change in transmitted light due to the detection pattern is detected. Based on this detection result, optical scanning is performed by correcting the deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium independently in the main scanning direction and the sub-scanning direction. 2. The optical scanning method according to claim 1, wherein the light-transmissive detection pattern is constituted by “a slit that is long in the sub-scanning direction and a slit that is long in a direction inclined with respect to the main scanning direction”. Based on the change in the light transmitted through, the deviation between the imaging position of the deflected light beam and the photosensitive medium surface is corrected in the main scanning direction,
The shift can be corrected in the sub-scanning direction based on a change in light transmitted through a slit that is long in a direction inclined with respect to the main scanning direction. Note that, in this specification, a slit in the detection pattern means a “slit-shaped translucent portion”.

Alternatively, the light transmissive detection pattern is constituted by “a single transmissive portion having a long side in the sub-scanning direction and a long side in a direction inclined with respect to the main scanning direction”.
Based on the change in transmitted light at the long side in the sub-scanning direction,
The deviation between the image forming position of the deflected light beam and the photosensitive medium surface is corrected in the main scanning direction, and based on a change in transmitted light in a long side in a direction inclined with respect to the main scanning direction, the deviation is corrected in the sub-scanning direction. Can be corrected (claim 3). In the optical scanning method according to claim 1, 2 or 3,
Two or more light beams are emitted from the light source to simultaneously scan a plurality of scanning lines, and the scanning line pitch can be detected based on the transmitted light by the light transmitting detection pattern. That is, the optical scanning method according to claim 4 is applied to a multi-beam scanning method, and together with adjustment of an image forming position,
The detection of the scanning line pitch is performed. Claims 1-4
In the optical scanning method described in any one of (1) and (2), it is preferable to stop the photosensitive medium when performing detection for correcting a deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium.

In the optical scanning method according to the fourth aspect, it is preferable that the photosensitive medium is stationary when detecting the scanning line pitch. Usually, the light scanning speed of the light spot in the light scanning is sufficiently faster than the moving speed of the photosensitive surface of the photosensitive medium in the sub-scanning direction. Although the pitch can be detected, as in the optical scanning method according to the fifth aspect, "when the imaging state of the deflected light beam is detected" or as in the sixth aspect, "on the photosensitive medium" When the scanning pitch of a plurality of light spots is detected in the above, the photosensitive medium is kept stationary, whereby the detection accuracy of the imaging state and the scanning line pitch can be further improved. 6. The optical scanning method according to claim 5, wherein the optical deflector included in the scanning optical system is a rotating mirror, and when performing detection for correcting a deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium, a rotation is performed. The rotational speed of the mirror can be reduced "(claim 7). Further, in the optical scanning method according to the sixth aspect, when the optical deflector included in the scanning optical system is a rotating mirror and the scanning line pitch is detected, "the rotational speed of the rotating mirror can be reduced". Claim 8). The “rotating mirror” is an optical deflector that deflects a light beam by rotating a deflecting and reflecting surface, and is specifically a rotating single-sided mirror, a rotating two-sided mirror, or a rotating polygonal mirror.

In the optical scanning method according to the fifth and sixth aspects, when the detection is performed, the rotation speed of the rotating mirror is reduced and the light scanning speed of the light spot is reduced because the photosensitive medium is stationary. Can perform highly accurate detection. In this case, since the light scanning speed is low, the response speed of the detecting means for detecting a change in transmitted light due to the detection pattern can be reduced, and the cost can be reduced. Also, since the light scanning frequency (the number of light scans per unit time) can be reduced,
Detection accuracy can be improved. Claims 1 to 7 above.
In the optical scanning method described in any one of the above, the optical deflector included in the scanning optical system is a rotating two-sided mirror or a rotating polygonal mirror, and is used to correct the deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium. In the optical scanning method according to claim 4 or 6, the scanning optical system can be configured such that "the same deflecting and reflecting surface is used within one cycle of detecting". When the scanning line pitch is detected by using a rotating dihedral mirror or a rotating polygonal mirror, the "deflection and reflection surface used in one cycle of the detection" can be set as the same. ). As described above, by making the deflecting and reflecting surfaces used in one cycle for performing detection the same, the detection accuracy is deteriorated due to the “light amount variation” of the light spot due to the variation in the reflectance on each deflecting and reflecting surface of the rotating mirror. Can be prevented.

In the optical scanning method according to any one of the first to tenth aspects, as a method for correcting a deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium, "a main light source and an optical deflector are provided. A first cylindrical lens having power only in the scanning direction and a second cylindrical lens having power only in the sub-scanning direction are provided to correct a deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium in the main scanning direction. Is performed by displacing the first cylindrical lens in the optical axis direction, and the shift in the sub-scanning direction can be corrected by displacing the second cylindrical lens in the optical axis direction (claim 11). Instead, for example, only the second cylindrical lens is provided, and the image formation position in the main scanning direction is corrected by a “coupling lens”. After imaging position adjustment, it is also possible to perform the image forming position adjustment of the sub-scanning direction by the displacement in the optical axis direction of the second cylindrical lens. However, the coupling lens is required to have “position accuracy with respect to the light source”, and there is a possibility of displacement of the optical axis due to the displacement. Therefore, it is necessary to carefully displace the coupling lens.

According to a twelfth aspect of the present invention, there is provided an optical scanning method comprising the steps of: "deflecting two or more light beams emitted from a light source by a scanning optical system and forming one or more light spots on a photosensitive medium; In the `` optical scanning method for optically scanning lines, '' a scanning pattern formed as a part of the photosensitive medium outside the image forming area of the photosensitive medium and detecting the light transmittance for detecting the scanning line pitch is scanned by each deflected light beam. Then, a change in transmitted light due to the detection pattern is detected, and a scanning line pitch is detected based on the detection result. This claim 1
Also in the optical scanning method described in 2, the detection pattern is “a long slit in the sub-scanning direction and a long slit in a direction inclined with respect to the main scanning direction” or “a long side in the sub-scanning direction and a long side in the main scanning direction. A single transmissive portion having a long side in a tilted direction '', and for the same reason as described above, it is preferable to keep the photosensitive medium stationary when detecting the scanning line pitch. When the optical deflector included in the scanning optical system is a rotating mirror, it is preferable to "slow down the rotating speed of the rotating mirror" when detecting the scanning line pitch. In the case of a polygon mirror, when detecting the scanning line pitch, “Detection 1
It is preferable that the same deflecting and reflecting surface is used in the cycle. "

According to a thirteenth aspect of the present invention, there is provided an optical scanning device, comprising: a step of deflecting at least one light beam emitted from a light source by a scanning optical system and forming at least one light spot on a photosensitive medium; An optical scanning device for optically scanning a line "has the following features. That is, there is provided an adjusting means for independently adjusting the image forming position of the light beam from the light source in the main scanning direction and the sub-scanning direction. In addition, a light-transmitting detection pattern for detecting a deviation between the image forming position of the deflected light beam in the main scanning direction and the sub-scanning direction and the surface of the photosensitive medium is provided on the photosensitive medium outside the image forming area. As a part of the medium, it is provided so as to be optically scannable by a deflected light beam. Further, a light receiving means for receiving a light beam transmitted through the detection pattern is provided,
Based on the output of the light receiving means, the control means controls the adjusting means such that "the deflected light beam forms an image on the surface of the photosensitive medium in the main scanning direction and the sub-scanning direction". In the optical scanning device according to the thirteenth aspect, the light-transmitting detection pattern may be constituted by “a slit that is long in the sub-scanning direction and a slit that is long in a direction inclined with respect to the main scanning direction”. And "a single transmissive portion having a long side in the sub-scanning direction and a long side in a direction inclined with respect to the main scanning direction".

In the optical scanning device according to the present invention, the light source emits two or more light beams, and the control means has a function of detecting a scanning line pitch. 16). In this case,
The optical scanning device has `` scanning line pitch adjusting means for adjusting the scanning line pitch '', and the control means `` controls the scanning line pitch adjusting means according to the detected scanning line pitch,
Function for correcting the scanning line pitch "(claim 17). 17. The optical scanning device according to claim 12, wherein the adjusting unit that independently adjusts the image forming position of the light beam from the light source in the main scanning direction and the sub-scanning direction includes a light source and an optical deflector. , A first cylindrical lens having power only in the main scanning direction and a second cylindrical lens having power only in the sub-scanning direction, and these first and second cylindrical lenses are independently illuminated. And a displacement means for displacing in the axial direction (claim 18). Claim 19
The optical scanning device described in the paragraph "The two or more light beams emitted from the light source are deflected by the scanning optical system, and
An optical scanning device which forms the above light spot and optically scans two or more scanning lines "has the following features.

That is, a scanning line pitch adjusting means for adjusting the scanning line pitch is provided. Further, on the photosensitive medium, a light transmission detection pattern for detecting a scanning line pitch is provided as a part of the photosensitive medium so as to be scannable by each deflected light beam. Further, a light receiving means for receiving the light beam transmitted through the detection pattern is provided. Then, based on the output of the light receiving unit, the scanning line pitch adjusting unit controls the scanning line pitch adjusting unit so that an appropriate scanning line pitch is obtained. According to a twentieth aspect of the present invention, there is provided a photosensitive medium used in the optical scanning device according to the thirteenth to eighteenth aspects, wherein "an image forming position of the deflected light beam in the main scanning direction and the sub-scanning direction outside the image forming area" And a light transmission detection pattern for detecting a deviation between the photosensitive medium and the surface of the photosensitive medium is provided as a part of the photosensitive medium so as to be optically scannable by a deflected light beam. " This photosensitive medium can be a "photoconductive photoreceptor" (claim 21). Claim 22
Is a photosensitive medium used in the optical scanning device according to claim 19, wherein "a light-transmitting detection pattern for detecting a scanning line pitch is provided outside the image forming area. As a part, it is provided so as to be able to optically scan with a deflected light beam. " This photosensitive medium can be a "photoconductive photoreceptor" (claim 23). The form of the photosensitive medium according to claims 20 to 23 is preferably a cylindrical form or an endless belt form.

The above-described detection pattern (a pair of a slit that is long in the sub-scanning direction and a slit that is long in a direction inclined with respect to the main scanning direction, a side that is long in the sub-scanning direction, The pattern formed by a single light transmitting portion that is long in the inclined direction can be formed repeatedly or continuously in the sub-scanning direction outside the image area of the photosensitive medium. The image forming apparatus according to the present invention is an “image forming apparatus that forms a latent image on a photosensitive surface of a photosensitive medium by optical scanning and visualizes the latent image to form a desired image”.
6). As the photosensitive medium, a silver halide film can be used. In this case, the latent image written on the photosensitive medium by optical scanning can be visualized according to a normal silver halide photographic process development / fixing method. Such an image forming apparatus can be implemented as an optical plate making apparatus, an optical drawing apparatus, or the like. Also, using a "photoconductive photoreceptor" as a photosensitive medium, forming an electrostatic latent image by its uniform charging and optical scanning,
The electrostatic latent image can be visualized as a toner image (claims 25 and 27). Such an image forming apparatus can be implemented as a digital copying apparatus or an optical printer. The toner image can be transferred and fixed on a sheet-like recording medium such as a transfer sheet or an OHP sheet (a plastic sheet for an overhead projector). Claim 24
The image forming apparatus described above uses an optical scanning device according to any one of claims 14 to 18 as an optical scanning device that performs optical scanning of a photosensitive medium. An image forming apparatus according to a twenty-sixth aspect uses the optical scanning device according to the nineteenth aspect as an optical scanning device for optically scanning a photosensitive medium.

In the optical scanning method according to any one of the first to eleventh and twelfth aspects, the method according to the thirteenth to the eighteenth aspects is described.
In the optical scanning device according to the nineteenth aspect, at the time of optical scanning, the deflection light beam transmitted through the detection pattern is detected, and the detection signal can be "used as a signal for optical writing synchronization".

[0016]

FIG. 1 is a diagram for explaining an embodiment of an optical scanning device according to the present invention. The optical scanning device of this embodiment is of a single beam type, and the light source 1 is a semiconductor laser. The divergent light beam emitted from the light source 1 is converted by the coupling lens 2 into a light beam form suitable for the subsequent optical system. In this embodiment, the coupling lens 2 converts a light beam incident from the light source 1 into a “convergent light beam”. The convergent light flux emitted from the coupling lens 2 enters the first cylindrical lens 3. The first cylindrical lens 3 has power "only in the main scanning direction". In this embodiment, the power of the cylindrical lens 3 is “negative power”. The cylindrical lens 3 converts the incident convergent light beam into a “light beam parallel to the main scanning direction” as a reference state. The cylindrical lens 3 is mounted on a displacement means 3A such as a stage, and can be displaced in the optical axis direction. The light beam transmitted through the cylindrical lens 3 (a parallel light beam in the main scanning direction and a convergent light beam in the sub-scanning direction) is incident on the second cylindrical lens 4. The second cylindrical lens has power only in the sub-scanning direction. In this embodiment, the cylindrical lens 4 has a positive power in the sub-scanning direction. For this reason, the light beam transmitted through the cylindrical lens 4 becomes a parallel light beam in the main scanning direction and a focused light beam in the sub-scanning direction, and is incident on the deflecting and reflecting surface of the rotary polygon mirror 5 as an optical deflector. At this time, the incident light beam forms an image near the deflecting reflection surface as a “long line image in the main scanning direction”.

The light beam reflected by the deflecting / reflecting surface becomes a deflecting light beam which is deflected at a constant angular velocity without being rotated at a constant speed in the direction of the arrow of the rotary polygon mirror 5, and is scanned by the scanning image forming optical system 6 (simplification of the drawing). Therefore, the scanning image forming optical system 6 is simplified.
Can be configured as a single lens as shown in the figure, can be configured with a plurality of lenses, or can be configured as a mirror having an image forming function, or a mixed system of a mirror and a lens) And is condensed as a light spot on the photosensitive surface of the photosensitive medium 7, which is the substance of the surface to be scanned, by the action of the scanning image forming optical system 6. In this embodiment, the photosensitive medium 7 is a “photoconductive photoconductor”. Therefore, it is hereinafter referred to as the photoconductor 7. The light spot performs main scanning by displacing the photosensitive member 7 in the main scanning direction (a direction parallel to the drawing) with the deflection of the deflected light beam. The scanning image forming optical system 6 has the “fθ function”
And makes the main scanning speed uniform. Here, FIG.
See Although the photoconductor 7 is formed in a cylindrical shape, the photoconductor 7 is used to detect a deviation between the imaging position of the deflected light beam in the main scanning direction and the sub-scanning direction and the surface of the photoconductor outside the “image forming area”. The light transmissive detection pattern 70 is provided as a “part of the photoconductor” so as to be optically scannable by a deflected light beam.

As shown in FIG. 1D, the detection pattern 7
Reference numeral 0 denotes a slit 71 (a slit-shaped light transmitting portion which is formed continuously) which is long in the sub-scanning direction (the rotation direction of the photoconductor 7) and a slit which is long in a direction inclined with respect to the main scanning direction. 72 (a slit-shaped light transmitting portion which is repeatedly formed in the sub-scanning direction). As shown in FIGS. 1A, 1C, and 1D, a light receiving unit 8 that receives a light beam transmitted through the detection pattern 70 is provided inside the photoconductor 7. The light receiving means 8 is provided in FIG.
As shown in (c) and (d), it is composed of a condenser lens 81 and a light receiving element 82. In this example, one light receiving means is shared by the slits 71 and 72,
If necessary, the light receiving means may be individually provided in each of the slits 71 and 72. Next, a description will be given of “correction of the deviation of the imaging position” for making the imaging position of the deflected light beam coincide with the surface of the photoconductor 7. FIG. 1E shows the light spot S
The state when P is displaced so as to cross the slit 71 in the main scanning direction is shown. In this figure, the light spot SP has a larger diameter in both the main scanning direction and the sub-scanning direction because the image forming position of the deflected light beam is shifted with respect to the photoconductor surface (that is, the slit 71).

FIG. 1E shows the output of the light receiving element 82 in the light receiving means 8 when the light spot SP crosses the slit 71. The axis is time and the vertical axis is output. The light spot SP "has a large diameter (therefore, the maximum light intensity of the light spot is small) in both the main scanning direction (left-right direction in the figure) and the sub-scanning direction."
Therefore, the output signal becomes a “broad-tailed mountain shape” having a low maximum output value. As shown in FIG. 1F, the shape of the light spot SP becomes “a state narrowed in the main scanning direction.
(Corresponding to the fact that the deflected light beam forms an image in the vicinity of the surface of the photoconductor in the main scanning direction) ", the output of the light receiving element 82 becomes large as shown in the right diagram of (f).
The base becomes narrow. 1 (g) and (h) show the light spot S
The state when P crosses the slit 72 in the main scanning direction,
The state of the output of the light receiving element 82 at this time is shown.
In (g), the light spot SP has a shape that is short in the main scanning direction and long in the sub-scanning direction. However, since the slit 72 is “inclined with respect to the main scanning direction”, the foot is widened to some extent. In (h), the light spot SP has a small diameter in both the main scanning direction and the sub-scanning direction (that is, the deflected light beam forms an image near the photosensitive surface in the main scanning and sub-scanning directions). The output of the element 82 has a shape with a large output peak and a narrow foot.

As shown in FIGS. 3E to 3H, when the maximum value of the output curve of the light receiving element 82 is P, and the output width when the output curve is cut by a "threshold" indicated by a broken line is t, P and t
Are inversely proportional to each other. For this reason, plotting the relationship between the above time: t or the reciprocal of P: 1 / P, and the “deviation amount” between the imaging position of the deflected light beam and the photosensitive surface, the deviation in the main scanning direction and the sub-scanning direction , A “curve with the minimum value” is obtained as shown in FIG.

Returning to FIG. 1A, when correcting the deviation between the image forming position of the deflected light beam and the photosensitive surface of the photosensitive member 7, the rotation of the photosensitive member 7 is stopped and the photosensitive member 7 is stopped. Is stopped, and at the same time, the optical scanning is repeated while the rotation speed of the rotary polygon mirror 5 is reduced. Each time light scanning is repeated,
A signal from (the light receiving element 82 of) the light receiving means 8 is input to a control unit 9 as a control means. The control unit 9 has a microcomputer and an input / output device. The control unit 9 drives the displacement unit 3A to displace the cylindrical lens 3 in the optical axis direction in accordance with a programmed control process according to the input signal from the light receiving unit 8. Since the cylindrical lens 3 “has power only in the main scanning direction”, this displacement changes the “image forming position in the main scanning direction” of the deflected light beam. The control unit 9 includes the cylindrical lens 3
For example, the above-mentioned time: t or "1 / P" is detected from the output from the light-receiving means accompanying the displacement of the sensor, and the displacement of the displacement means 3A is controlled so that these take the minimum value. As a result, when the minimum value is realized, the deflected light beam forms an image on the photosensitive surface in the main scanning direction.

After the correction of the image forming position in the main scanning direction is completed in this way, the displacement means 4A is controlled to displace the cylindrical lens 4 in the optical axis direction. The displacement of the displacement means 4A is controlled so that "1 / P" takes the minimum value. When the minimum value is realized in this way, the deflected light beam forms an image on the photosensitive surface in both the main scanning and sub-scanning directions, and the minimum spot diameter is realized in both the main and sub-scanning directions. become. Note that, instead of the above-described control, the following may be performed. That is, for each of the main scanning direction and the sub-scanning direction, a characteristic curve as shown in FIG. 1 (i) is set in advance by measurement, and this is stored in the control unit, and the optical scanning (cylindrical lens) of the detection unit is performed twice. From the optical scanning results at the reference positions 3 and 4 and the optical scanning results when displaced from the reference position by a predetermined position, the “correction displacement amount” of each cylindrical lens
May be obtained by calculation or a table, and the respective cylindrical lenses 3 and 4 may be displaced based on the correction displacement amount thus obtained. Although the case where the slit 71 corrects the image forming position in the main scanning direction and the slit 72 corrects the image forming position in the sub-scanning direction has been described above, the image forming position in the main and sub-scanning direction can be corrected using only the slit 72. it can. However, the accuracy of the correction is higher when the slits 71 and 72 are used.

FIG. 2 is a diagram for explaining another embodiment of the optical scanning device. In order to avoid complication, the same components as those in FIG. 1A are denoted by the same reference numerals as those in FIG. 1A, and description thereof will be omitted. In the optical scanning device shown in FIG. 2A, the optical scanning device is of a “multi-beam type”, and a plurality of light beams are emitted from the light source 1A. The number of light fluxes emitted from the light source 1 is appropriately two or more. Such a light source 1A can be realized as a well-known "light source using a semiconductor laser array" or "light beam from an independent semiconductor laser using a beam combining prism" as a light source of a multi-beam scanning device. . In the following description, it is assumed that two light beams are emitted from the light source 1A for the sake of simplicity. These two light fluxes are deflected by a “scanning optical system” constituted by optical elements from the coupling lens 2 to the scanning image forming optical system 6, and are “deflected in the sub-scanning direction” on the photosensitive surface of the photoconductor 7. The light is condensed as "two light spots separated from each other", and two scanning lines are simultaneously optically scanned.

The "difference between the imaging position of each deflected light beam and the photosensitive surface" is corrected by the same method as described with reference to FIG. In this case, the correction is performed on “appropriate” of the two deflected light beams. Then, the other deflection light beam is automatically corrected. In the optical scanning device of FIG.
The detection and correction of the scanning line pitch are performed. When the correction for this is performed, the photoconductor 7 is stopped and the rotation speed of the rotary polygon mirror 5 is reduced. FIG.
(B) shows a slit 71 constituting the detection pattern 70;
FIG. 72 shows a state where two light spots SP1 and SP2 cross in the main scanning direction. Light spot SP1,
SP2 is the main scanning direction and the sub-scanning direction (vertical direction in the figure)
Are separated, the corner slit 72, a main scanning direction: since tilted by theta, time the light spot SP1 crosses between slits 71, 72: and T _1, the light spot SP
The time when ₂ crosses between the slits 71 and 72 is different from T2. Light scanning speed of light spots SP1 and SP2: v
Can be uniquely given as a condition for detection. Then, when the above-mentioned times: T ₁ and T ₂ are known, the scanning line pitch is obtained by “(T ₁ −T ₂ ) v × tan θ”. That is, the control unit 9 as a control unit, based on the output of the light receiving unit 8,
Time: T ₁ and T ₂ are obtained, and calculation is: (T ₁ −T ₂ ) v × tan
By performing θ, the scanning line pitch of the currently performed multi-beam scanning is detected.

When the detected result is different from "the originally set scanning line pitch", the control section 9 controls the scanning line pitch adjusting means 10 to correct the scanning line pitch to an appropriate size. The scanning line pitch adjusting means 10 includes, for example,
It can be configured as a “mechanism for rotating the light source 1A around the optical axis of the coupling lens 2” or a mechanism for changing the imaging magnification by displacing the entire light source 1A in the optical axis direction of the coupling lens.

Although a combination of two slits 71 and 72 has been described above as a detection pattern, a detection pattern as shown in FIG. 3A can also be used (a possibility of confusion). 1 and 2, the photoreceptor is designated by the reference numeral 7. The detection pattern 73 has a light transmission property of "a long side in the sub-scanning direction and a side in the main scanning direction. A single transmissive portion having a long side in the inclined direction (in the example of the figure, such a pattern repeats in the sub-scanning direction, is formed continuously, and is connected to the side inclined in the main scanning direction. 3B shows a state where two light spots SP1 and SP2 cross the detection pattern 73 in the main scanning direction. The light spots SP1 and SP2 are shown in FIG. Are the main scanning direction and sub-scanning direction (Fig. Are separated in the vertical direction), the angular to one side 73b in the main scanning direction of the detection pattern 73: theta
The light spot SP1 is located at the side 73a, 7
Time traverse between 3b: the T _1, the light spot SP2 is side 7
3a, time crossing between 73b: are different from each other and T _2.
Since v is a set value, time: the optical scanning speed of the light spot SP1, SP2 when T _1, T ₂ is become known, the scanning line pitch determined by _{"(T 1 -T 2) v ×} tanθ ".

The control unit 9 serving as control means includes a light receiving means 8
Based on the output of ( ₁₎ , the times: T ₁ and T ₂ are obtained, and the operation: (T ₁
−T ₂ ) v × tan θ to detect the scanning line pitch of the currently performed multi-beam scanning. In addition, using the detection pattern 73, it is possible to detect the deviation between the image forming position of the deflected light beam and the photosensitive surface. As shown in FIG. 3C, the light spot SP (the light spots SP1 and S
When P2 (appropriate one of P2) scans the detection pattern 73 in the main scanning direction, the output from the light receiving means 8 is as shown in the upper diagram of FIG. In other words, the output increases as the light spot SP crosses the long side 73a of the detection pattern 73 in the sub-scanning direction and becomes a constant value, and then the output in the direction 73b inclined with respect to the main scanning direction. It decreases gradually by crossing. The rise and fall of this output signal may be monitored. For example, when the output is differentiated, the result is as shown in the lower diagram of FIG. The time T, which is the interval between the top of the peak and the bottom of the valley in this figure, is:
These correspond to T ₁ and T ₂ .

The height of the peak in the lower part of FIG. 3D: P1
Changes depending on the deviation between the image forming position of the deflected light beam in the main scanning direction and the photosensitive surface, and becomes maximum when the image forming position in the main scanning direction coincides with the photosensitive surface. , Height: the cylindrical lens 3 so that P1 is maximized.
By controlling and adjusting the position, the image forming position of the deflected light beam in the main scanning direction can be matched with the photosensitive surface of the photosensitive member 7. Similarly, the depth P2 of the valley in the lower part of FIG. 3D changes in accordance with the deviation between the image forming position of the deflected light beam in the sub-scanning direction and the photosensitive surface, and the image forming position in the sub-scanning direction becomes photosensitive. If the position of the cylindrical lens 4 is controlled and adjusted so that the depth: P2 becomes the maximum, the image forming position of the deflected light beam in the sub-scanning direction is adjusted to the photosensitive surface of the photosensitive member 7. Can be matched. Instead of the above, for each of the height: the reciprocal of P1: 1 / P1 and the depth: the reciprocal of P2: 1 / P2, graph data as described in FIG. The displacement amount of the cylindrical lenses 3 and 4 may be determined based on these.

FIG. 4 shows another embodiment of the optical scanning device. Also in this figure, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted. This embodiment is an optical scanning device of a multi-beam system similar to the embodiment shown in FIG. The difference from the embodiment of FIG. 2 is that in the embodiment of FIG. 4, the deviation between the image forming position of the deflected light beam and the photosensitive surface of the photoconductor 7 is not corrected, and the detection and correction of the scanning line pitch are not performed. Is to do. The detection and correction of the scanning line pitch are performed in exactly the same manner as in the embodiment of FIG. The detection pattern 73 described with reference to FIG. 3 can be used as the detection pattern.

FIG. 5 shows an embodiment of the image forming apparatus. The image forming apparatus 100 is a laser printer. The laser printer 100 has a photoconductive photoconductor 111 formed in a cylindrical shape as a photosensitive medium. A charging roller 1 serving as a charging unit is provided around the photoconductor 111.
12, a developing device 113, a transfer roller 114, and a cleaning device 115 are provided. A well-known "corona charger" can be used as the charging means. As the photoreceptor, a “belt-shaped one” can be used. An optical scanning device 116 using a laser beam is provided, and an image is written between the charging roller 112 and the developing device 113 by “exposure by optical scanning”. As the optical scanning device 116, those described in the embodiment with reference to FIGS. 1, 2, and 4 can be appropriately used.

In FIG. 5, reference numeral 117 denotes a fixing device, and reference numeral S denotes a transfer sheet as a “sheet-shaped recording medium”. When performing image formation, the photoconductive photoconductor 111
Is rotated clockwise at a constant speed, and the surface thereof is
2 to form an electrostatic latent image upon exposure to the laser beam from the optical scanning device 116 by optical writing.
The formed electrostatic latent image is a so-called “negative latent image”, and the image portion is exposed. This electrostatic latent image is reversely developed by the developing device 113 to form a toner image on the photoconductor 111. The transfer paper S is superimposed on the toner image at the transfer portion while being transported in the direction of the arrow, and
The toner image is electrostatically transferred. The transfer paper S on which the toner image has been transferred is fixed with the toner image by the fixing device 117 and is discharged out of the device. The surface of the photoconductor 111 after the transfer of the toner image is cleaned by the cleaning device 115 to remove residual toner, paper dust, and the like. The above-described “OHP sheet” or the like can be used instead of the transfer paper, and the transfer of the toner image can be performed via an “intermediate transfer medium” such as an intermediate transfer belt.

When the optical scanning device of the embodiment shown in FIG. 1 is used, the deflected light beam is emitted in both the main scanning direction and the sub-scanning direction.
Since optical scanning can be performed while an image is formed on the photosensitive surface of the photoconductor 111, high-density excellent writing can be performed. When the optical scanning device of the embodiment shown in FIG. 2 is used, the deflecting light beam is emitted in both the main scanning direction and the sub-scanning direction.
An image can be formed on the photosensitive surface of the photoconductor 111 and multi-beam scanning can be performed at an appropriate scanning line pitch, and high-density and good writing can be performed. As an optical scanning device, FIG.
By using the embodiment, multi-beam scanning can be performed at an appropriate scanning line pitch, and good writing can be performed.

The optical scanning device described in the embodiment with reference to FIGS. 1 and 2 emits one or more light beams emitted from the light sources 1 and 1A by the scanning optical systems 2, 3, 4, 5, and 6. In an optical scanning device that deflects and forms one or more light spots on the photosensitive medium 7 and optically scans one or more scanning lines, the image forming position of the light flux from the light sources 1 and 1A is defined as the main scanning direction. Adjustment means 3, 3A, 4, independently adjusting in the sub-scanning direction;
4A, a light-transmissive detection pattern 70 for detecting a deviation between the image forming position of the deflected light beam in the main scanning direction and the sub-scanning direction and the surface of the photosensitive medium, outside the image forming area of the photosensitive medium 7, As a part of the photosensitive medium 7, light scanning is provided by a deflecting light beam, and a light receiving means 8 for receiving a light beam transmitted through the detection pattern 70 is provided. An optical scanning device (claim 13) in which the control means 9 controls the adjusting means 3, 3A, 4, 4A so as to form an image on the surface of the photosensitive medium in the sub-scanning direction. Is formed by a slit 71 that is long in the sub-scanning direction and a slit 72 that is long in a direction inclined with respect to the main scanning direction (claim 14). Main scan Adjustment means for adjusting independently in the scanning direction and the sub-scanning direction is provided between the light sources 1 and 1A and the optical deflector 5, and the first cylindrical lens 3 having power only in the main scanning direction and only in the sub-scanning direction. A second cylindrical lens 4 having power and the first and second
(1) is constituted by displacement means (3A, 4A) for independently displacing the cylindrical lens in the optical axis direction.
8).

As described with reference to FIG. 3, the side 73a long in the sub-scanning direction is used as the light transmissive detection pattern.
And a detection pattern 73 composed of a single transmissive portion having a long side 73b in a direction inclined with respect to the main scanning direction (claim 15). In the optical scanning device shown in the embodiment in FIG. 2, the light source 1A emits two or more light beams, and the control means 9 has a function of detecting a scanning line pitch (claim 16). . The control unit 9 has a scanning line pitch adjusting unit 10 for adjusting the scanning line pitch, and the control unit 9 controls the scanning line pitch adjusting unit 10 according to the detected scanning line pitch to correct the scanning line pitch. It has a function (claim 17). The optical scanning device of the embodiment shown in FIG. 4 deflects two or more light beams emitted from the light source 1A by the scanning optical systems 2, 3, 4, 5, and 6 and emits one light beam on the photosensitive medium 7. In an optical scanning device that forms the above light spot and optically scans two or more scanning lines, a scanning line pitch adjusting means 10 for adjusting the scanning line pitch
A light-transmitting detection pattern 70 (73) for detecting a scanning line pitch is provided outside the image forming area of the photosensitive medium 7 as a part of the photosensitive medium so as to be scannable by each deflected light beam. A light receiving unit 8 for receiving a light beam transmitted through the detection pattern 70 (73) is provided. Based on an output of the light receiving unit 8, an appropriate scanning line pitch is obtained.
Scanning line pitch adjusting means 1 by scanning line pitch controlling means 9
0 is controlled (claim 19).

The photosensitive medium 7, which has been described with reference to FIGS. 1 and 3, has an image forming position in the main scanning direction and the sub-scanning direction of the deflected light beam and the surface of the photosensitive medium outside the image forming area. Pattern 70 for detecting light transmissivity for detecting deviation from
(73) is provided as a part of the photosensitive medium 7 so as to be optically scannable by a deflected light beam (claim 20).
It is a photoconductive photoconductor (claim 21). The photosensitive medium 7 used in the optical scanning device of the embodiment shown in FIG. 4 also has a light transmitting detection pattern 70 (73) for detecting a scanning line pitch outside the image forming area. As a part, it is provided so as to be optically scannable by a deflected light beam (Claim 22) and is a photoconductive photoconductor (Claim 2).
3). According to the optical scanning device shown in FIGS. 1 and 2, one or more light beams emitted from the light sources 1 and 1A are deflected by the scanning optical systems 2 to 6 and In an optical scanning method in which one or more light spots are formed and one or more scanning lines are optically scanned, the light is formed as a part of the photosensitive medium 7 outside the image forming area of the photosensitive medium 7 and the main scanning direction of the deflected light beam and A light-transmissive detection pattern 70 for detecting a shift between the image forming position in the sub-scanning direction and the surface of the photosensitive medium is optically scanned with a deflected light beam, and the detection pattern 7 is detected.
0, a change in transmitted light due to zero, and based on the detection result, a deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium 7 is independently corrected in the main scanning direction and the sub-scanning direction to perform optical scanning. The method (claim 1) is performed.

The light transmitting detection pattern 70 is
A slit 71 that is long in the sub-scanning direction and a slit 72 that is long in a direction inclined with respect to the main scanning direction. Based on a change in light transmitted through the long slit 71 in the sub-scanning direction,
The deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium 7 is corrected in the main scanning direction, and the deviation is corrected in the sub-scanning direction based on a change in light transmitted through the slit 72 that is long in a direction inclined with respect to the main scanning direction. An optical scanning method for correcting the direction is implemented (claim 2). Further, as shown in FIG. 3, the light-transmitting detection pattern 73 is constituted by a single transmissive portion having a long side 73a in the sub-scanning direction and a long side 73b in a direction inclined with respect to the main scanning direction. Then, based on the change in the transmitted light at the long side 73a in the sub-scanning direction, the deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium is corrected in the main scanning direction and tilted with respect to the main scanning direction. An optical scanning method (claim 3) that corrects the shift in the sub-scanning direction based on a change in transmitted light at the side 73b long in the direction can be implemented.
Further, according to the optical scanning device shown in FIG. 2, two or more light beams are emitted from the light source 1 </ b> A, and a plurality of scanning lines are simultaneously optically scanned. Based on this, an optical scanning method for detecting the scanning line pitch is performed.

As described in the embodiment shown in FIGS. 1 to 3, when the detection for correcting the deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium 7 is performed, The medium 7 is stopped (Claim 5), and in the optical scanning method implemented by the optical scanning device of FIG. 2, the photosensitive medium 7 is stopped when the scanning line pitch is detected (Claim 6). 1 and 2, the optical deflector 5 included in the scanning optical system is a rotating mirror. In the optical scanning method performed by this device, the image forming position of the deflected light beam and the surface of the photosensitive medium When performing the detection for correcting the deviation, the rotation speed of the rotating mirror is reduced (claim 7), and the scanning line pitch is detected in the optical scanning method implemented by the optical scanning device of FIG. At this time, the rotation speed of the rotating mirror 5 is reduced (claim 8).
1 and 2, the optical deflector 5 is a rotary polygon mirror, and is used to detect a deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium. Is performed, the same deflecting / reflecting surface is used in one cycle for performing the detection (claim 9). Even when detecting the scanning line pitch, the same deflecting / reflecting surface is used in one cycle for performing the detection. (Claim 10).

In the optical scanning method implemented by the optical scanning apparatus shown in FIGS. 1 and 2, a first cylindrical lens 3 having power only in the main scanning direction is provided between the light sources 1 and 1A and the optical deflector 5. A second cylindrical lens 4 having power only in the sub-scanning direction is provided. The first cylindrical lens 3 is moved in the optical axis direction to correct the deviation between the imaging position of the deflected light beam and the surface of the photosensitive medium in the main scanning direction. The correction in the sub-scanning direction is performed by displacing the second cylindrical lens 4 in the optical axis direction. In the optical scanning device of FIG. 4, two or more light beams emitted from the light source 1A are
An optical scanning method in which light is deflected by the scanning optical systems 2 to 6 and formed as one or more light spots on the photosensitive medium 7 and optically scans two or more scanning lines. A light-transmitting detection pattern 70 (7) formed as a part of the photosensitive medium for detecting the scanning line pitch
3) is scanned by each deflected light beam, a change in transmitted light due to the detection pattern is detected, and a scanning line pitch is detected based on the detection result (claim 12).

The image forming apparatus shown in FIG. 5 is an image forming apparatus which forms a latent image on a photosensitive surface of a photosensitive medium 111 by optical scanning and visualizes the latent image to form a desired image. 1 and 2 as the optical scanning device 116.
Each optical scanning device described in the embodiment is used.
4) It is also possible to use the optical scanning device shown in the embodiment in FIG. 42 (Claim 26). The photosensitive medium 111 is a photoconductive photosensitive member, and the electrostatic latent image is formed on the photosensitive medium 111. It is formed by uniform charging and optical scanning and is visualized as a toner image (claims 25 and 27).

[0040]

As described above, according to the present invention, a novel optical scanning method, optical scanning device, photosensitive medium, and image forming apparatus can be realized. Since the photosensitive medium of the present invention has a "detection pattern" as a part thereof outside the image forming area, the optical scanning method / optical scanning apparatus using this photosensitive medium requires optical component errors, assembly errors, and temperature / humidity fluctuations. Etc., the "deviation between the imaging position of the deflected light beam and the surface of the photosensitive medium"
Correction can be accurately performed independently in the main scanning direction and the sub-scanning direction, and optical scanning can be performed with an appropriate light spot. Further, since the transmitted light of the photosensitive medium is directly detected, it is possible to accurately correct the imaging position deviation regardless of the positional accuracy between the scanning optical system and the photosensitive medium. Further, in the case of performing the multi-beam optical scanning, “correction of the positional deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium” and / or “correction of the scanning line pitch” are performed to achieve good multi-beam scanning. Can be realized.
Further, the image forming apparatus of the present invention can realize good image formation by writing an image using the optical scanning device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating one embodiment of an optical scanning device.

FIG. 2 is a diagram for explaining another embodiment of the optical scanning device.

FIG. 3 is a diagram for describing one embodiment of a photosensitive medium.

FIG. 4 is a diagram for explaining another embodiment of the optical scanning device.

FIG. 5 is a diagram for explaining an embodiment of the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Coupling lens 3 1st cylindrical lens 4 2nd cylindrical lens 5 Rotating polygon mirror 6 Scanning optical system 7 Photoconductor 8 Light receiving means

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Claims (27)

[Claims] An optical scanning method for deflecting one or more light beams emitted from a light source by a scanning optical system, forming one or more light spots on a photosensitive medium, and optically scanning one or more scanning lines. A light transmission formed outside the image forming area of the photosensitive medium as a part of the photosensitive medium and for detecting a deviation between an image forming position of the deflected light beam in the main scanning direction and the sub-scanning direction and a surface of the photosensitive medium; The scanning pattern is optically scanned with a deflecting light beam to detect a change in transmitted light due to the detection pattern. Based on the detection result, the deviation between the imaging position of the deflecting light beam and the surface of the photosensitive medium is determined in the main scanning direction and the sub-scanning direction. An optical scanning method, wherein optical scanning is performed by independently correcting in a scanning direction. 2. The optical scanning method according to claim 1, wherein the light-transmissive detection pattern includes a slit that is long in the sub-scanning direction and a slit that is long in a direction inclined with respect to the main scanning direction. Based on the change in the light transmitted through the long slit in the direction, the deviation between the imaging position of the deflected light beam and the surface of the photosensitive medium,
An optical scanning method, wherein the shift is corrected in the main scanning direction, and the shift is corrected in the sub-scanning direction based on a change in light transmitted through a slit elongated in a direction inclined with respect to the main scanning direction. 3. The optical scanning method according to claim 1, wherein the light-transmissive detection pattern has a single transmission side having a long side in the sub-scanning direction and a long side in a direction inclined with respect to the main scanning direction. The shift between the imaging position of the deflected light beam and the photosensitive medium surface is corrected in the main scanning direction based on the change in the transmitted light at the long side in the sub-scanning direction. An optical scanning method characterized in that the shift is corrected in the sub-scanning direction based on a change in transmitted light in a long side in a direction inclined with respect to the direction. 4. The optical scanning method according to claim 1, wherein two or more light beams are emitted from a light source, a plurality of scanning lines are simultaneously optically scanned, and the light is transmitted to a light-transmitting detection pattern. An optical scanning method, wherein a scanning line pitch is detected based on the detected value. 5. The optical scanning method according to claim 1, wherein the detection of the deviation between the imaging position of the deflected light beam and the surface of the photosensitive medium is performed by stopping the photosensitive medium. An optical scanning method comprising: 6. The optical scanning method according to claim 4, wherein when detecting the scanning line pitch, the photosensitive medium is kept stationary. 7. The optical scanning method according to claim 5, wherein the optical deflector included in the scanning optical system is a rotating mirror, and detection for correcting a deviation between the image forming position of the deflected light beam and the surface of the photosensitive medium is performed. In some cases, the rotation speed of the rotating mirror is reduced. 8. The optical scanning method according to claim 6, wherein the optical deflector included in the scanning optical system is a rotating mirror, and the rotation speed of the rotating mirror is reduced when detecting a scanning line pitch. An optical scanning method characterized by the above-mentioned. 9. An optical scanning method according to claim 1, wherein the optical deflector included in the scanning optical system is a rotating two-sided mirror or a rotating polygonal mirror, and the image forming position of the deflected light beam and the light sensitivity are adjusted. An optical scanning method, wherein when performing detection for correcting a deviation from the medium surface, the same deflecting and reflecting surface is used within one cycle of performing detection. 10. The optical scanning method according to claim 4, wherein the optical deflector included in the scanning optical system is a rotary dihedral mirror or a rotary polygonal mirror, and when the scanning line pitch is detected, the detection is performed. Wherein the same deflecting and reflecting surface is used within one cycle of performing the light scanning. 11. The optical scanning method according to claim 1, wherein a first cylindrical lens having power only in the main scanning direction is provided between the light source and the optical deflector; And a second cylindrical lens having power only
Correction of the deviation in the main scanning direction between the imaging position of the deflected light beam and the surface of the photosensitive medium is performed by displacing the first cylindrical lens in the optical axis direction, and correction of the deviation in the sub-scanning direction is performed in the second scanning direction. An optical scanning method, wherein the method is performed by displacing a cylindrical lens in an optical axis direction. 12. An optical scanning method for deflecting two or more light beams emitted from a light source by a scanning optical system, forming one or more light spots on a photosensitive medium, and optically scanning two or more scanning lines. A scanning pattern formed by a part of the photosensitive medium outside the image forming area of the photosensitive medium, the light transmitting detection pattern for detecting a scanning line pitch, being scanned by each deflection light beam; A scanning line pitch based on the detection result. 13. An optical scanning device for deflecting one or more light beams emitted from a light source by a scanning optical system, forming one or more light spots on a photosensitive medium, and optically scanning one or more scanning lines. An adjusting means for independently adjusting the image forming position of the light beam from the light source in the main scanning direction and the sub-scanning direction; and outside the image forming area of the photosensitive medium, the main scanning direction and the sub-scanning direction of the deflected light beam. A light transmissive detection pattern for detecting a shift between the image forming position and the surface of the photosensitive medium is provided as a part of the photosensitive medium so as to be optically scannable by a deflected light beam, and receives a light beam transmitted through the detection pattern. The adjusting means is controlled by the control means based on the output of the light receiving means so that the deflected light beam forms an image on the surface of the photosensitive medium in the main scanning direction and the sub-scanning direction. An optical scanning device, comprising: 14. The optical scanning device according to claim 13, wherein the light-transmissive detection pattern is constituted by a slit that is long in the sub-scanning direction and a slit that is long in a direction inclined with respect to the main scanning direction. Optical scanning device. 15. The optical scanning device according to claim 13, wherein the light transmissive detection pattern has a single transmission side having a long side in the sub-scanning direction and a long side in a direction inclined with respect to the main scanning direction. An optical scanning device, comprising: an optical scanning device; 16. An optical scanning device according to claim 13, wherein said light source emits two or more light beams, and said control means has a function of detecting a scanning line pitch. Optical scanning device. 17. The optical scanning device according to claim 16, further comprising scanning line pitch adjusting means for adjusting a scanning line pitch, wherein the control means controls the scanning line pitch adjusting means according to the detected scanning line pitch. An optical scanning device having a function of correcting a scanning line pitch. 18. An optical scanning device according to claim 13, wherein said adjusting means for independently adjusting an image forming position of a light beam from a light source in a main scanning direction and a sub-scanning direction comprises: A first cylindrical lens having power only in the main scanning direction, a second cylindrical lens having power only in the sub-scanning direction, and the first and second cylindrical lenses. An optical scanning device comprising: a displacement unit that independently displaces in an optical axis direction. 19. An optical scanning device which deflects two or more light beams emitted from a light source by a scanning optical system, forms one or more light spots on a photosensitive medium, and optically scans two or more scanning lines. In the above, provided a scanning line pitch adjusting means for adjusting the scanning line pitch, outside the image forming area of the photosensitive medium, as a part of the photosensitive medium, a light transmissive detection pattern for detecting the scanning line pitch, In addition to providing a scan with a deflected light beam,
A light receiving means for receiving a light beam transmitted through the detection pattern is provided. Based on an output of the light receiving means, the scanning line pitch control means controls the scanning line pitch adjusting means so that an appropriate scanning line pitch is obtained. An optical scanning device, comprising: 20. A photosensitive medium used in the optical scanning device according to claim 13, wherein an image forming position of the deflected light beam in the main scanning direction and the sub-scanning direction, a surface of the photosensitive medium, A photosensitive medium, characterized in that a light-transmissive detection pattern for detecting a deviation of the photosensitive medium is provided as a part of the photosensitive medium so as to be optically scannable by a deflected light beam. 21. The photosensitive medium according to claim 20, which is a photoconductive photosensitive member. 22. A photosensitive medium used in the optical scanning device according to claim 19, wherein a light transmitting detection pattern for detecting a scanning line pitch is formed outside the image forming area as a part of the photosensitive medium. A photosensitive medium provided so as to be capable of optically scanning with a deflected light beam. 23. The photosensitive medium according to claim 22, which is a photoconductive photosensitive member. 24. An image forming apparatus for forming a latent image by optical scanning on a photosensitive surface of a photosensitive medium and visualizing the latent image to form a desired image. Claim 12
An image forming apparatus using the optical scanning device according to any one of (1) to (18). 25. The image forming apparatus according to claim 24, wherein the photosensitive medium is a photoconductive photosensitive member, and the electrostatic latent image is formed by uniform charging of the photosensitive medium and optical scanning, and is visualized as a toner image. An image forming apparatus, comprising: 26. An image forming apparatus for forming a latent image by optical scanning on a photosensitive surface of a photosensitive medium and visualizing the latent image to form a desired image. Claim 19
An image forming apparatus using the optical scanning device according to any one of the preceding claims. 27. The image forming apparatus according to claim 26, wherein the photosensitive medium is a photoconductive photoreceptor, and the electrostatic latent image is formed by uniform charging of the photosensitive medium and optical scanning, and is visualized as a toner image. An image forming apparatus, comprising: